Run-flat device

ABSTRACT

A run-flat device ( 13 ) for fitting on the outer circumference of a wheel ( 11 ) inside an inflatable tire ( 12 ). The device ( 13 ) comprising an annular ring ( 14 ) made up of a plurality (preferably three) of arcuate segments ( 15 ) interconnected at each end by clamping means ( 23, 23   a   , 23   b   , 28, 29, 35 ) equally spaced around the ring that imparts to each segment ( 15 ) a circumferential clamping force and an axial clamping force to urge the segments circumferentially and axially towards each other.

BACKGROUND OF THE INVENTION

This invention relates to vehicle wheels that have inflatable tyres andin particular to devices that are fitted on the rim of a wheel insidethe tyre to enable the wheel to run with a deflated tyre. Such deviceswill hereinafter be called “run-flat devices”. The present invention isconcerned with clamping devices for clamping together segments of asegmented ring run-flat device.

With conventional wheels that are not fitted with run-flat devices, whenthe tyre becomes deflated the tyre becomes damaged and can becomeshredded or thrown off the metal wheel rim. This can cause the vehicleto which the wheel is fitted to loose control, thus endangering otherroad users. At best, the vehicle can be stopped and the wheel replacedwith a spare wheel, or the puncture repaired, or a new tyre fitted tothe existing wheel. For commercial vehicles, such as lorries, this isvery time consuming and costly because of the need to acquire specialistbreakdown or repair services to get the vehicle back on the move again.

With lorries, military vehicles, carriers, such as bullion carriers,security vehicles, or other vehicles where a puncture of a tyreeffectively halts the vehicle, and exposes the vehicle to danger from anexternal threat, there is a need to be able to continue with the vehiclejourney irrespective of the deflated tyre.

When a tyre deflates partially or completely, the effective diameter ofthe wheel with the deflated tyre becomes relatively smaller comparedwith the wheels with inflated tyres. Therefore, the frictionalengagement of the deflated tyre on the road causes the peripheral speedof the deflated tyre to increase to match the peripheral speed of theinflated tyres.

Simultaneously, any differential gearbox in the transmission drive pathto a wheel with a deflated tyre will divert torque away from the drivenwheels that have inflated tyres to the wheel with the deflated tyre.This in turn causes rotation of the deflated tyre relative to the metalwheel, particularly where the metal wheel is a driven wheel.

SUMMARY OF THE INVENTION

Run-flat devices that fit on the rim of the metal wheel inside the tyreare well known, and usually comprise an annular body on to which thatpart of the outer circumferential wall of the tyre that is in contactwith the ground or road can contact. The annular body is usually made intwo parts that are clamped to the outer rim of the metal wheel and theannular body is designed to slip circumferentially on the metal rim whenthe tyre deflates. This slippage is important because it allows the tyreto slip on the wheel rim whilst ensuring little or no slippage of thetyre relative to the outer circumference of the annular body.

In a prior known device, the annular body comprises two semi-circularsegments that are pivotally connected together at each end by a singleclamping bolt that clamps the two segments together. Radial clamping ofthe segments onto the metal wheel is achieved by a cylindrical bandextending around the circumference of the segments that can be tightenedto pull the segments together prior to tightening the pivot bolts. Inthis case the pivotal connection at one end of the segments has anelongate slot through which the clamping bolt passes that allowscircumferential movement of the segments relative to each other duringclamping them on to the rim of the metal wheel. The bolt is accessiblefor tightening from only one side of the segments.

In a second prior known form of run-flat device having two segments, asingle circumferential clamping means is used at one end of thesegments. At the other end a simple pivot is provided. The clampingmeans comprises a slot in one of the segments, and the slot has aninclined surface. A tapered wedge is provided in the slot and engagesthe inclined surface. A single bolt (accessible from one side) passesthrough holes in each end of adjoining segments. At least one of theholes is elongated to allow relative circumferential movement of thesegments. By tightening the single clamping bolt, the two ends of thesegments are pulled together by the wedge to clamp them on to the rim ofthe metal wheel.

A problem with both of these known types of segmented run-flat devicesis that because a single bolt is used at at least one end of thesegments, each segment can pivot relative to the other and move out ofalignment radially relative to the other segment. This can cause damageto the inside surface of the outer circumferential wall of the tyre whenthe tyre becomes deflated. This is particularly more of a problem withthe prior known run-flat devices that do not use circumferentialclamping bands because the two segments tend to open up like jaws undercentrifugal and centripetal loads. At worst, even when the tyre isinflated, the leading edge of one segment can protrude beyond thecircumference of an adjoining segment of the protruding segment andrelease the frictional engagement of the annular body on the rim of themetal wheel, allowing relative rotational slippage of the run-flatdevice on the rim of the metal wheel. Consequently, excessive wear onthe run-flat device and the rim of the metal wheel is caused and thewheel becomes unbalanced during normal running. When the tyre deflates,the protruding edges of the displaced segments exacerbate the damage tothe inside of the tyre and can cause the annular body to twist out ofalignment with the plane of rotation of the wheel. This may lead to thetyre coming off the metal wheel altogether.

A further disadvantage of known segmented run-flat devices is that eachsegment has a single captive bolt that is only accessible from one sideof the segments, and the segments are of an asymmetric shape, with thedesign of one end of each segment being different from the other end ofthe same segment. This means that two different sets of segments have tobe made depending on whether the segments are to be fitted to theleft-hand side or to the right-hand side of the vehicle. This adds tothe complexity and cost of manufacture and means that extra spare setshave to be carried by puncture repairers or breakdown personnel.

A further object of the present invention is to provide a run-flatdevice comprising a plurality of segments that are inter-connected byclamping means that restricts relative pivotal movement between thesegments.

A further object of the present invention is to provide clamping meansfor an annular run-flat device comprising a plurality of arcuatesegments in which there is provided circumferentially spaced clampingmeans around the annular device at each connection between the segments.

A further object of the present invention is to provide a clamping meansfor segmented run-flat devices that restrict the pivotal movement of thesegments relative to each other.

BRIEF DESCRIPTION OF SEVERAL VIEWS OF THE DRAWINGS

The present invention will now be described, by way of an example, withreference to the accompanying drawings in which:

FIG. 1 shows a cross-sectional view through a wheel fitted with arun-flat device incorporating the present invention;

FIG. 2 is a side elevation showing a segmented ring and inner sleeve ofthe run-flat device of FIG. 1;

FIG. 3 is a schematic perspective view of the run-flat device of FIG. 1;

FIG. 4 shows a cross sectional view through the ends of two adjacentsegments of the run flat device of FIG. 2 and shows in greater detailthe clamping means of the present invention;

FIG. 5 shows a schematic cross-sectional view of an inner sleeve of therun-flat device of FIG. 2; and

FIG. 6 shows a run flat device of FIGS. 1 to 5 fitted to a two partwheel.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS OF THE INVENTION

Referring to FIG. 1, there is shown schematically a cross-sectionthrough a wheel assembly of a lorry. The wheel assembly 10 comprises ametal wheel 11 that is constructed so as to be capable of being fixed toa wheel hub of a vehicle (not shown) by way of conventional studs andnuts (not shown), or threaded studs (not shown). An inflatable tyre 12is mounted on the rim of the metal wheel in a conventional manner. Themetal wheel is of a single piece construction of the type in widespreaduse, and is provided with a conventional inflation valve (not shown).The metal wheel could be made of a well-known two-part construction thathas a removable rim as shown in FIG. 6.

Mounted on the rim of the wheel 11 inside the tyre 12 is a run-flatdevice 13 comprising an annular body 14 made of three nylon segments 15that are either clamped directly to the outer diameter of the wheelrims, or, as is preferred, is clamped to the outer circumference of aninner sleeve 16 that is split so as to permit the inner sleeve 16 to beopened and snapped in place around the outer diameter of the wheel 11.The inner sleeve 16 is made of nylon, but it could be constructed with anylon central band 17 and polyurethane edge bands 18 as shown in FIG. 5.The central band has a dove-tail shaped recess 17(a) on each side faceand the polyurethane side bands 18 each have a dove-tail shaped sidemember 18(a) that fits into one of the recesses 17(a). The central band17 provides rigidity to resist side-loads of the side walls as theycollapse inwards whilst the polyurethane side bands 18 provide rigiditywith slightly more flexibility or resilience than the nylon central band17 to cushion the contact between the beads of the side-walls of thetyre 12 to avoid damage to the tyre 12 when the tyre deflates.

The outer circumference of the central band 17 has a recess 41 and theinner circumference of the segments 15 have a flange 42 that locates inthe recess 41. A lubricant may be provided between the outercircumference of the inner sleeve 16 and the inner circumference of thesegments 15.

It will be appreciated that at high rim speeds, the run-flat device 13is subject to centripetal and centrifugal forces which tend to loosenthe circumferential grip of the run-flat device 13 on the metal wheel11. A shear pin 43 may be provided (as shown in FIG. 5) for each segment15 to accommodate this radial movement whilst restraining the segments15 circumferentially until the pins 43 are sheared by the deflated tyrecontacting the segments 15 and causing the segments 15 as a completering to rotate. The shear pin 43 is inserted through a hole in thecentral part of the rim of the wheel and through the inner sleeve 16.

The inner circumference of the inner sleeve 16 may be profiled to matchthe profile of a specific metal wheel, or could simply bridge across therecesses or wells of the metal wheel 11 between the surfaces 12(a),12(b) on which the beads of the side walls of the tyre 12 sit. The innersleeve 16 must be shaped so as not to impede the fitting of the tyrebecause it is necessary to provide gaps or circumferential recesses thatallow each side wall of the tyre 12 to fit as the tyre is slipped overthe front rim of the metal wheel 11 prior to inflation. The inner sleeve16 functions as a tyre bead retainer that stops the sidewalls of thetyre 12 collapsing inwards when the tyre is deflated.

Referring now to FIG. 6 there is shown a second type of metal wheel 11fitted with a run-flat device 13 of the present invention. In thisdesign of wheel, the metal wheel 11 is in two parts 44 and 45. The mainpart 44 of the wheel constitutes the rear rim 46 and central rim 47 ofthe wheel 11 on to which the rear wall of the tyre 12 is fitted and thesecond part 45 constitutes the front rim 48 that retains the front sidewall of the tyre 12. The second part 45 is bolted to the main part 44 ofthe wheel prior to inflation of the tyre 12. The run-flat device 13 isof a similar construction to that described and shown in FIGS. 2 to 5.

It will be appreciated that the inner sleeve 16 shown in FIG. 1effectively blocks off the deep wells formed in the rim of the metalwheel and serves to stop the side walls of the tyre falling into thedeep wells when the tyre deflates. Clearly in those designs of metalwheel that do not have deep wells and those that have cylindrical orslightly conical central rims with in-built bead retaining features(such as for example similar to that shown in FIG. 6) the inner sleeve16 may be dispensed with but in this case a bead retaining device may beneeded or the inner periphery of the segments modified to form a beadretaining device. We prefer to keep the inner sleeve 16 as the beadretainer.

Referring in greater detail to FIGS. 2 and 3, the three segments 15 aresymmetrical about a radial plane orthogonal to the axis of rotation ofthe wheel and are of identical shape whether for a left-hand wheel or aright-hand wheel. Each segment is a segment of a hollow cylinder with aconcave end 20 and a convex end 21. The convex ends 21 are of acomplementary shape to the concave ends 20 so that the convex end 20 ofeach segment 15 nestles into the concave end 21 of an adjacent segment15. The segments 15 are assembled inside the tyre 12 with the convexends 21 constituting the leading edge relative to the direction ofrotation of the tyre 12 when it is running wholly deflated. Each segment15 has an arcuate recess 22 on each side to lighten the segments.

At each end of the segments 51 there is provided a clamping means 23constructed in accordance with the present invention in the form of twoparallel bolts 23(a), 23(b). The shape of the ends of adjacent segments15 and details of the clamping means is best seen in FIG. 3.

Referring to FIGS. 2, 3 and 4, the concave end 20 of each segment has aflange 26 of half the thickness of each segment and twocircumferentially spaced holes 24, 25 are drilled through the flange 26.The holes 24 are of a slightly larger diameter than that of the bolts23(a) and 23(b) to allow relative movement of the end 20 relative to end21. The convex end 21 of each segment has a flange 27 that overlaps theflange 26 in a circumferential direction. The flange 27 is provided withan elongate slot 28 that has inclined surfaces 29 that face away fromthe concave end 20 of the adjacent segment 15.

A wedge 31 having an inclined face 32 that abuts the inclined face 29 ofthe slot 28 in the convex end 21 of the segment 15 is placed in the slot28 with the inclined face of the wedge 31 in contact with the inclinedfaces 29. The wedge 31 has a hole 31(a) through which one of thedome-headed clamping bolts 23(a) is passed. The ends 21 of the segmentshave two spaced holes 33, 34 that align with the holes 24, 25 in ends20. Two captive nuts 35 are mounted on a retaining plate 36 and the nuts35 are inserted into the holes 33, 34 in the flanges 27. By tighteningthe first bolt 23(a) the wedge 31 urges the ends of the segmentstogether in a circumferential direction. A second dome headed clampingbolt 23(b) is passed through a hole 37 in a clamping plate 38, throughthe slot 28 and holes 34 and screwed into the second captive nut 35.

The clamping plate 38 bridges the slot 28 and is shaped so as not tointerfere with bolt 23(a). When bolt 23(b) is tightened the clampingplate 38 engages a sidewall of the segment (15) and pulls the twoflanges 26, 27 axially together in a direction parallel to the axis ofrotation of the wheel 11.

To fit the run-flat device 13, the rear side wall of the tyre 12 islevered on to the front rim of the metal wheel 11 and then the innersleeve 16 is prised open and fitted over the rim of the metal wheelinside the deflated tyre 12. The slit 39 in the inner sleeve 16 ispositioned to align with the inflation valve of the wheel (not shown).The rear wall of the tyre is then pushed over the sleeve 16 on to therear rim. The segments 15 are inserted into the cavity of the deflatedtyre from the front and are loosely assembled around the inner sleeve 16with the heads of the bolts 23(a), 23(b) facing outwards. The wedges 31are then tightened down by tightening the bolts 23(a) evenly, and thiscauses the wedges 31 to pull the segments 15 together and thereby clampthe segments 15 firmly to the inner sleeve 16 and clamp the inner sleeve16 to the rim of the metal wheel 11. With the run-flat device 13 clampedon to the rim of the metal wheel 11 the bolts 23(b) are fully tightenedto clamp the flanges 26 and 27 together axially. The outer sidewall ofthe tyre 12 is then levered over the front rim of the metal wheel 11 andthe tyre 12 inflated.

In use, when the tyre 12 deflates, the tyre 12 collapses onto the outercircumferential surface of the run-flat device 13 in the region wherethe tyre 12 contacts the ground or road. This causes the run-flat device13 to slip circumferentially on the rim of the metal wheel 11. Thisslippage between either the segments 15 and the rim of metal wheel(where no inner sleeve 16 is fitted) or between the segments 15 and theinner-sleeve 16 (where a sleeve 16 is fitted), ensures that there islittle or no relative rotation between the tyre 12 and the run-flatdevice 13 and consequently little or no damage to the tyre 12. The beadsof the sidewalls of the tyre 12 are prevented from collapsing inwards bythe inner sleeve 16 that acts as a bead retainer when the tyre deflates.

It will be appreciated that at high rim speeds, the run-flat device 13is subject to centripetal and centrifugal forces, which, in the absenceof the second bolt 23(b) would loosen the circumferential grip of therun-flat device 13 on the metal wheel 11 by allowing the segments 15 topivot relative to each other. By using two parallel bolts 23(a), 23(b)pivotal movement of the segments relative to each other is restricted orprevented. The bolts 23(a), 23(b) also provide both clamping in thecircumferential direction and clamping in the axial direction (in adirection along the axis of rotation of the wheel) and prevent thesegments twisting out of alignment with the wheel 11 when the deflatedtyre contacts the outer circumference of the run-flat device 13.

1. A run-flat device for fitting on the outer circumferences of a wheelinside an inflatable tyre, said device comprising an annular ring madeup of a plurality of arcuate segments having a flange at each end thatoverlaps circumferentially the corresponding flanges of adjacentsegments, which flanges are interconnected by clamping means equallyspaced around the ring that imparts to each segment a circumferentialclamping force and an axial clamping force to urge the segmentscircumferentially and axially towards each other wherein the clampingmeans comprises a first and second clamping bolts which pass through apair of spaced holes formed in the adjacent flanges, said deviceadditionally comprising a retaining plate having two captive nutsmounted thereon, for securing the first and second clamping bolts and toprevent lateral twisting of the flanges, and a clamping plate spacedremotely from said retaining plate and shaped so as not to interferewith one of said clamping bolts, wherein the clamping means furthercomprises a slot provided in one of the flanges at one end of eachsegment that includes an inclined surface that faces away from theimmediately adjacent segment, a wedge provided in the slot, said wedgehaving an inclined surface that contacts the inclined surface of theslot, and having a hole that aligns with a first hole of the pair ofspaced holes in the flanges, and a first such clamping bolt that passesthrough the first hole of the pairs of holes and the hole in the wedgewhereby tightening of the said first bolt causes the wedge to urge thesegments towards each other circumferentially, and the clamping meansfurther includes the second such clamping bolt substantially parallel tothe first bolt, said second bolt passing through the second hole of thepair of holes in the flanges and through said clamping plate in contactwith a side face of the segment whereby tightening of the second boltclamps the flanges of the segments together axially, and the combinedclamping effect of the two bolts restricts pivotal movement of thesegments relative to each other, and wherein the captive nuts arelocated within the first and second holes.
 2. A run-flat deviceaccording to claim 1 wherein there is provided a split inner sleeve forfitment to the rim of the wheel and onto the outer circumference ofwhich the segments sit.
 3. A run-flat device according to claim 1wherein there is provided a split inner sleeve for fitment to the rim ofthe wheel and onto the outer circumference of which the segments sit. 4.A run-flat device according to claim 1 wherein there is provided a splitinner sleeve for fitment to the rim of the wheel and onto the outercircumference of which the segments sit.
 5. A run-flat device accordingto claim 2 wherein the inner circumference of the inner sleeve isprofiled to match the profile of the outer circumference of the wheel.6. A run-flat device according to claim 3 wherein the innercircumference of the inner sleeve is profiled to match the profile ofthe outer circumference of the wheel.
 7. A run-flat device according toclaim 4 wherein the inner circumference of the inner sleeve is profiledto match the profile of the outer circumference of the wheel.
 8. Arun-flat device according to claim 2 wherein the outer circumference ofthe inner sleeve has a recess, and each segment has a flange on itsinner circumferential surface that engages in the recess on the innersleeve.
 9. A run-flat device according to claim 3 wherein the outercircumference of the inner sleeve has a recess, and each segment has aflange on its inner circumferential surface that engages in the recesson the inner sleeve.
 10. A run-flat device according to claim 4 whereinthe outer circumference of the inner sleeve has a recess, and eachsegment has a flange on its inner circumferential surface that engagesin the recess on the inner sleeve.
 11. A run-flat device according toclaim 2 wherein the inner sleeve comprises a central band and two sidebands made of a material that is more resilient than the material of thecentral band.
 12. A run-flat device according to claims 11 wherein thecentral band is made of nylon.
 13. A run-flat device according to claim11 wherein the side bands are made of polyurethane.
 14. A run-flatdevice according to claim 1 wherein the segments are identical in shape.15. A run-flat device according to claim 1 wherein the segments areidentical in shape.
 16. A run-flat device according to claim 1 whereinthe segments are identical in shape.
 17. A run-flat device according toclaim 2 wherein a shear pin is provided between the inner sleeve andeach of the segments to resist circumferential movement of the sleevesrelative to the inner sleeve during normal running of the wheel.